Container for high-pressure fluids



D. MAPES CONTAINER FOR HIGH PRESSURE FLUIDS March 6, 1945,

Fil ed Feb. 15,

INVENTOR mil/WEI. M PES,

ATTORNEY Patented Mar. 6, 1945 UNITED STATES PATENT OFFICE CONTAINER FORHIGH-PRESSURE FLUIDS Daniel Mapes, Rutherford, N. J., assignor toSpecialties Development Corporation, Bloomfield, N. J a corporation ofNew Jersey Application February 15, 1941, Serial No. 379,037

7 3 Claims.

This invention broadly relates to cylinders or containers for'gaseousfluid media, and more speciflcally to cylinders or containers adapted tohold fluid media under high pressures.

The high pressure media most commonly used are carbon dioxide, oxygen,nitrogen and hydrogen, and, while their individual practicalapplications are quite numerous, the best known uses are for thecarbonation of fluids, fire extinguishing, inflation of inflatabledevices, power actuation and welding.

An increasingly important application of high pressure fluid media isthat to aircraft, and particularly to combat planes where the use ofcarbon dioxide fire extinguishing, flotation, emergency raft inflation,and the emergency operation of hydraulic equipment, the use of oxygenfor high altitude breathing, and various other uses of high pressurefluid media have made the high Pressure gas container an indispensableaccessory.

Containers for high pressure fluid media have been made in a number ofways, but are usually of seamless construction, and where suchcontainers are to be shipped by common carriers in interstate commerce,they are required to meet regulations issued by the Interstate CommerceCommission. While such containers intended for use on aircraft areusually of lighter weight than those for other uses, as for examplecontainers made in accordance with Letters Patent of the United StatesNo. 2,026,133, containers meeting the requirements of the InterstateCommerce Commission are made with a consider-able factor of safety, andcan withstand pressures of two to three or more times the normal workingpressure of the contained fluid medium.

Up until the relatively recent past, it was not thought necessary togive any special consideration to the construction of these containersfor use on combat planes. However, in view of the practically universalmilitary acceptance of highpowered, high-caliber machine gun ammunition,or, to be more precise, the supplanting of 0.30 by 0.50 caliber bulleton military aircraft, new hazards have arisen, not heretofore present.Thus, cylinders containing high pressure fluids, struck by 0.50 caliberbullets, in contrast to the effect of a 0.30 bullet, generally burstwith a violent explosion, naturally dam-aging the airplane andendangering its occupants.

It has been observed in the course of numerous tests, which wereundertaken to determine the exact nature of the behavior of suchcontainers when struck by bullets, flying shrapnel or the like, that acylindrical container of the type referred to, when squarely hit on itscylindrical portion, will permit the bullet to enter, usually leaving around opening, but will literally rip wide open longitudinally at thepoint of exit of the bullet, the internal pressure being efl'ectual incompleting the failure of the cylinder wall begun by the bullet. This isin consonance with the known fact that once a piece of material, such assteel, has been partially deformed Or has suffered an initial localrupture, such piece will require a much smaller force to be completelyruptured than if no such initial rupture had been sustained. 'An

analysis of the performance of the tested cylinders I disclosed that theeffect of the bullet on the container wall was most pronounced at thepoint of the bullet exit, as in that case the bullet was assisted by theaction of the internal fluid pressure.

Since the strengthening of the cylinder walls by an increase in theirthickness, although possibly effective in stopping or slowing thebullet, would render such containers too heavy for practical use, andespecially for aircraft application, it occurred to me to providesupporting means for the cylinder wall, which, while it might be injuredor locally destroyed by the bullet, would support the uninjured portionsof the wall adjacent to the bullet hole, thus, effectively preventingthe further tearing of the cylinder. The supporting means, therefore,would preferably be in the nature of a form of jacket means with a highstrength-to-weight ratio as one of its prerequisites. After lengthyexperimentation with various methods of protection, it was found thatthe method of winding the cylinders externally with high tensile pianosteel wire, properly secured, afforded a really positive protection,while its comparative light weight, its adaptability for productionpurposes, and its cheapness pointed to its being a solution well adaptedto the requirements of these cylinders and their application.

It is therefore an object of this invention to provide means which willlend strength against bursting to the walls of high pressure fluidmedium containers at a time only when said walls have been deformedlyweakened.

It is also an object of this invention to provide a means for minimizingthe destructive effects on high pressure fluid medium containersproduced thereon when they are struck by bullets, flying shrapnel orother projectiles propelled at a high velocity.

' It is a further object to provide high pressure fluid mediumcontainers with gun flre protection jacket means of the type referred towithout appreciably adding to the weight of the containers.

These and other objects will become apparent as the description proceedswith reference to the accompanying drawing, in which:

Figure 1 is an elevational view, partly in section, illustrating acontainer for high pressure fluid media, protected in accordance withthe present invention.

Figure 2 is a perspective view of a portion of the container,illustrating one of the wire winding retaining rings.

Figure 3 is a fragmentary view of a wire retaining ring, showing amethod of anchoring the ends of the wire.

Figure 4 is a fragmentary sectional view of the retaining ring showingits arrangement with respect to the cylinder and the layers of wire.

Figure 5 is a fragmentary elevational view, illustrating another methodof protecting containers by layers of wire.

Referring now to the drawing, wherein the same references are used forthe same elements, i refers to a conventional metallic high pressurefluid container having a generally cylindrical form and a hemisphericalshoulder and closed end, and initially strong enough to withstand apressure higher than the normal operating pressure and in accordancewith the acceptance tests of the Interstate Commerce Commission. Theshoulder is provided with an opening terminating in a necked-in portion2, into which is threadedly secured a fiuid control device 3, and whichmay take a y one of numerous valve forms in accordance with theapplication desired.

At 4 is indicated a jacket for the cylindrical portion of the container,which is formed in this case of a double layer winding of high tensilestrength steel wire, commonly known as piano wire," and which is appliedunder varying degrees of tension. The relation between the cylinder walland the double layer winding is clearly seen at 5, where the containeris broken away to reveal the wall and the jacket in section. The wirewinding may be secured by various methods, and is here shown, by way ofillustration, as being held in place at its ends by means of retainingrings 6. In Figure 2, such a ring may be seen to have a flange '1 and tobe split as at 8. Apertures 9 in the flange provide anchorage for thefree wire ends, as more clearly shown in Figure 3, where an elevationalview of a section of a retaining ring 6 indicates how the beginning IDof the wire winding is looped into one of the apertures, and the end ofthe winding H is anchored in the other opening. The double layer windingis continuous and comprises, in this instance, one forward and onereturn winding.

.When the wire is completely in place, the flange I is bent inwardly, asis apparent from Figure 4, which illustrates a section of the cylinderwall, the retaining ring and the wire jacket. In order to assure thestability of the entire jacket, its surface is solder-licked, that is,covered with a relatively thin though coherent coat of solder, indicatedby reference numeral 13.

Figure 5 illustrates a variation of the winding of Figure 1, insofar asthe layers are wound so as to form an angle with respect to each other.

Under operating conditions, it has been the experience that anunprotected cylinder, charged with a high pressure fluid medium, whenhit by a bullet, will be pierced, if fired on at fairly close range,both through the front and rear walls. With 0.50 caliber fire, forinstance, the entrance hole is generally round, taking the shape of theentering bullet. Seldom, if ever, do splits or fractures occur at theentrance hole. However, at tht exit hole, the cylinder, due to the factthat the metal of the wall is pushed outwardly by the impact of theoutgoing bullet, will, in practically all cases, develop cracksradiating from the hole. These local cracks are sufllcient to permit thehigh pressure medium to rip the cylinder wide open, producing theequivalent of a violet explosion. These cracks about the bullet exithole apparently so weaken the cylinder that the hoop stress generated bythe pressure in the cylinder far exceeds the resistance of the steel.The mere fact that the homogeneity of the steel is impaired by the holeand the fissures radiating therefrom, renders adjacent sections of themetal much less stressresistant than they would be normally, even thoughthey might be thicker there than at an uninjured place. This is inaccord with the wellknown theory of elasticity that the unit stresses inthe section of a member under load immediately adjacent a hole or grooveare a multiple of what they are in the member as a whole. By wrappinghigh tensile piano wire, which has, say, a tensile strength of about400,000 pounds per square inch in the sizes used, around the cylindricalportion of the cylinder, preferably with each coil touching the next,and extending the wrapping or winding substantially from the junction ofthe hemispherical bottom or closed end to the junction of thehemispherical shoulder, as shown in the illustrative embodiment of theinvention, additional strength is lent to the cylindrical wall sectionat the time of a sudden tress due to piercing of the containers by abullet or other projectile. A hole or crack in the cylinder wall,therefore, once started by a bullet or other projectile on its way outthrough the container, is effectively prevented from developing into adestructive tear by the reenforcement given to the metal adjacent thetear by the coils of piano wire or other suitable reenforcement, sincethe undamaged turns are able to exert their full and undiminishedstrength. In this, they may be aided by the manner in which the wire iswound, as for example shown in Figure 6, where the angularity of onelayer of the winding with respect to the other indicated here, has theeffect that the bullet in passing through breaks any single coil in oneplace only, assuming, of course that the cylinder'is hit squarely,unless it be in a certain range adjacent the short axis of the nowelliptical coil. This is in contrast to the double break which the coilsin the line of the passing bullet sustain, when wound in accordance withigure 1.

In the matter of securement of the winding, it has been found desirableto give adjacent coils of the wire a certain amount of cohesion, as wellas a preset, that is, coil the wire with a radius somewhat smaller thanthat of the container so that the wire, even if severed locally, willresist any tendency to unravel, and, by being made to grip the cylinder,will properly function to reenforce the cylinder wall at the time ofgreatest stress. Thin, adherent coatings of various materials, appliedover the winding, are capable of achieving such coherence, theillustrated method of "solderlicking being a practical and satisfactoryexample.

The' cylindrical portion of the container is about half as strong inbursting as the hemispherical dome and bottom, since the container as awhole is of uniform wall thickness because of regulations and formanufacturing reasons. It is primarily, therefore, this cylindricalsection which needs reenforcement. This has been proven in numeroustests, which showed, when the bottom or dome of the container is hit byrepresentative caliber machine gun bullets, that the container will notrupture. The preferred method, therefore, is to apply such protection tothe cylindrical section of the container, starting and endingapproximately at the junctions of the spherical with the cylindricalsurfaces, a. procedure which has proven quite satisfactory.

The invention, however, contemplates the use also of other types ofjacket means varying in their structure and composition, in accordancewith requirements and circumstances. Similarly, the invention may beapplied to various types of high pressure fluid containers, which differin their method of fabrication, structure, material or wall thickness.While such other jacket means variations are possibly not as effectiveas the methods specifically described, their use is determined bypreference and they clearly fall within the scope of the presentinvention. It is, therefore, as an exemplifying embodiment of theinvention, for a clearer emphasis of the purpose and scope thereof, thatcontainers normally capable of withstanding the stresses produced by theinternal pressure, and constructed substantially in accord with therules of the Interstate Commerce Commission, and their protection by thepreferred methods mentioned above, have been adduced here.

It has of course been proposed to construct containers for fluid mediaout of relatively thinwalled containers wrapped with wire to strengthenthe containers against bursting under only normal operating pressures;but my invention difiers therefrom in that it is concerned withprotecting containers, which are normally sumciently strong to safelywithstand normal operating pressures, against unusual bursting stressesdeveloped when such containers are struck or pierced by machine gunfire, flying shrapnel or other projectiles propelled at a high velocity.Actually, the problem of protecting high pressure fluid media containersagainst gunfire and the like is a problem more particularly occasionedby present-day warfare, not only because of the greater destructivepower of modern weapons, but also because of the relatively recent butwidespread use of high pressure fluid media containers on warplanes withthe attendant danger of violent bomb-like explosions of such containerswhen struck or pierced by high velocity projectiles. This problem thepresent invention solves in a way not previously contemplated, byreenforcing containers which are otherwise normally sufficiently strongto safely withstand desired p. erating pressures against the destructiveforces which arise only when such containers are struck or pierced byhigh velocity projectiles. It must therefore be constantly kept in mindthat the containers for which jacketing means in accordance with thepresent invention are provided, are quite capable by themselves ofresisting normal internal fluid pressures, and that the jacketing meansas such acquires significance and comes into action only when abnormalstresses are developed upon striking or piercing of the containers.

The present invention may also be utilized not only to providereenforcement to the cylinder wall immediately adjacent any weakenedportion thereof and to counteractthe incidentally increased localstresses, but also at the same time to hold such incidental stresses toa minimum by conditioning the initial state of stress in the cylinderwall. Thus, by increasing the tension under which the reeni'orcing wireor other type of jacketing means is secured over the cylinder, thecylindrical wall may be put under pre-compression, so that both thenormal stress in the cylindrical wall due to the normal pressure'of thecontained medium and the abnormal stress developed when the wall isstruck or pierced, may be counteracted and reduced.

From the foregoing description, it will be seen that I have provided gunfire protective means for containers for high pressure fluid media inaccordance with the objects enumerated above, and that while theinvention has been described with reference to specific embodiments ofthe invention, it will be evident to one skilled in the art that theobjects of the invention may be achieved through other forms withoutdeparture from the spirit and the scope thereof, and for this reasonI-do not wish to be strictly limited to the forms of this disclosure butrather to the scope of the appended claims.

I claim:

1. A container for storing a high pressure fluid medium comprising aone-piece substantially rigid seamlessly formed metallic cylinderinherently subject to ripping apart when pierced by a projectile, saidcylinder havinga cylindrical wall of substantially uniform shape andthickness provided with substantially smooth inner and outer surfaces,and being of a thickness to withstand the highest working pressures atwhich the fluid medium may be confined in said cylinder under normalconditions of use without further reenforcement; a continuous winding ofonly two layers of contiguous convolutions of steel pianowire of hightensile strength woundunder tension on said cylindrical wall, said wirehaving been given a preset prior to being wound on said cylindricalwall, said preset establishing convolutions of slightly smaller innerdiameter than the outer diameter of said cylindrical wall whereby saidconvolutions tend to embrace said cylindrical wall in clasping relationto minimize and localize the area of rupture of said cylinder and toprevent ripping apart of said cylinder when said cylindrical wall ispierced by a projectile; a split ring at each end of said cylindricalwall, said split rings having a flange extending under the endconvolutions of said windings and having a second flange folded over theend convolutions of said winding to secure the end convolutions, one ofsaid rings securing both free ends of said winding; and a coating ofsolder applied to said winding serving to secure adjacent convolutionsand aiding the preset condition of the coils in resisting the tendencyfor the wire to unravel when severed by a projectile.

2. A container for storing a high pressure fluid medium comprising aone-piece substantially rigid seamlessly formed metallic cylinderinherently subject to ripping apart when pierced by a projectile, saidcylinder having a cylindrical wall of substantially uniform shape andthickness provided with substantially smooth inner and outer surfaces,and being of a thickness to withstand the highest working pressures atwhich the fluid medium may be confined in said cylinder under normalconditions of use without further reinforcement; a continuous winding ofno more than two layers of contiguous convolutions of steel piano-wireof high tensile strength wound under tension on said cylindrical wall,said wire having been given a preset prior to being wound on saidcylindrical well, said preset establishing convolutions of slightlysmaller inner diameter than the outer diameter of said cylindrical wallwhereby said convolutions tend to embrace said cylindrical wall inclasping relation to minimize and localize the area of rupture of saidcylinder and to prevent ripping apart of said cylinder when saidcylindrical wall is pierced by a projectile; a split ring at each end ofsaid cylindrical wall, said split rings having a flange extending underthe end convolutions of said windings and having a second flange foldedover the end convolutions of said winding to secure the endconvolutions; and a coating of adherent material applied to said windingadhering thereto and serving to secure adjacent convolutions and aidingthe preset condition of the coils in resisting the tendency for the wireto unravel when severed by a projectile.

3. A container for storing a high pressure fluid medium comprising aone-piece substantially rigid seamlessly formed metallic cylinderinner-- ently subject to ripping apart when pierced by a projectile,said cylinder having a cylindrical wall of substantially uniform shapeand thickness provided with substantially smooth inner and outersurfaces, and being of a thickness to withstand the highest workingpressures at which the fluid medium may be confined in said cylinderunder normal conditions of use without further reenforcement; acontinuous winding of no more than two layers of contiguous convolutionsof steel piano-wire of high tensile strength wound under tension on saidcylindrical wall, said wire having been given a preset prior to beingwound on said cylindrical wall, said preset establishing convolutions ofslightly smaller inner diameter than the outer diameter of saidcylindrical wall whereby said convolutions tend to embrace saidcylindrical wall in clasping relation to minimize and localize the areaof rupture of said cylinder and to prevent ripping apart of saidcylinder when said cylindrical wall is pierced by a projectile; meansfor retaining said winding on said cylinder; and a coating of adherentmaterial applied to said winding adhering thereto and serving to secureadjacent convolutions and aiding the preset condition of the coils inresisting the tendency for the wire to unravel when severed by aprojectile.

DANIEL MAPES.

